overriding

This might be a simple question for many but has confused me. I am picking an example from Kathy Sierra that shows the utility of Abstract Classes but I am unable to understand the overall importance of abstract classes. Example We have an abstract class Car with abstract methods - power() & topSpeed() . These methods are implemented in sub classes BMW , Volkswagen and Audi . My question is - why do we need to have the abstract class Car in the first place to customize methods for each car type? Why not have these two methods in any one of these car subtypes, say BMW and then other two -

Is there a way to make a particular cell read-only/write protected in python xlwt? I know there's is a cell_overwrite_ok flag which does not allow to overwrite contents of cells (all cells) but can this be done on cell by cell basis. Thanks, Sun Excel cells have a locked attribute that is enabled by default. However, this attribute is only invoked when the worksheet's protection attribute is also set to True . If the worksheet is not protected, the locked attribute is ignored. Therefore, your question isn't best framed as how to make cells read-only . Rather, the question is how to make cells

I have 2 bundles and i want to override the repository of one of them in the other : I have a source bundle : SourceBundle. I have my override bundle : OverrideBundle First, in OurVendorOverrideBundle.php, I added : public function getParent() { return 'SomeVendorSourceBundle'; } Then I wanted to add a custom method for the repository of an entity of SourceBundle. The source entity is Response.php, and its repository is ResponseRepository.php So i did : <?php namespace OurVendor\OverrideBundle\Repository; use Doctrine\ORM\EntityRepository; use SomeVendor\SourceBundle\Repository

I'm now focusing on a project requiring insight of Java byte code. With the help of bcel , I can now complete most of the work. One point that I'm now not clear is how to identify a sub-class method override its base code? Is there any attribute recorded in the .class file associated with a method indicating this overriding relationship or should I go backwards to its base class can compare method signatures? Any hints will be highly appreciated. You need to look up the hierarchy chain--there's nothing in the byte code that indicates it's an overridden method, because there doesn't need to be.

I would like to override console.log and call it on my new function. I try something like this but I get Uncaught TypeError: Illegal invocation : console.log = function() { this.apply(window, arguments); }.bind(console.log); console.log('as'); This is my goal: console.error(exception); should do: console.error = function() { if (typeof exception.stack !== 'undefined') { console.error(exception.stack); } else { console.error.apply(windows, arguments); } }.bind(console.error); console.error('as'); console.error({stack: 'my stack....'}); EDIT: Actually, it works in firefox and not in Chrome... It

I have an ActiveSupport::Concern module which looks roughly like the following: module MyModel module Acceptance extend ActiveSupport::Concern included do enum status: [:declined, :accepted] end def declined! self.status = :declined # some extra logic self.save! end def accepted! self.status = :accepted # some extra logic self.save! end end end This is only ever going to be included into ActiveRecord classes, hence the use of enum . Basically, I'm overriding the declined! and accepted! methods that are created by ActiveRecord::Enum.enum with some extra, custom logic of my own. The problem is,

This question already has an answer here: C++ virtual override functions with same name 4 answers The title is probably confusing. Suppose we have the following set up; class A { public: virtual void fn() = 0; }; class B { public: virtual int fn() {}; }; class C: public A, public B { }; Is there any way to define A::fn in class C ? No . This is not possible. It will always conflict with either of the fn() . The syntax of fn() are different, void fn(); // in A and in B is, int fn(); // in B You have to make those syntax same in A and B to let C implement the fn() . Demo . There's no way in C to